For the purpose of preventing oxygen oxidation and performing long-term storing of various goods tending to be affected by oxygen and accordingly deteriorated or degraded, typified by food, beverages, pharmaceuticals and cosmetics, there have been used oxygen absorbing agents performing removal of oxygen in the vessels containing these goods.
As oxygen absorbing agents, from the viewpoint of the oxygen absorbing capacity, easiness in handling and safety, there have generally been used oxygen absorbing agents including iron powder as the main reaction agent. However, such iron-based oxygen absorbing agents responds to metal detectors, and hence it has been difficult to use metal detectors for foreign matter inspection. Packages enclosing iron-based oxygen absorbing agents have possibility of ignition and hence cannot be heated with microwave ovens. In addition, the oxidation reaction of iron powder needs moisture, and hence iron-based oxygen absorbing agents have been able to develop the oxygen absorption effect thereof only for the objects to be stored which are high-moisture systems.
By constituting vessels and the like with multilayer materials having oxygen absorbing layers composed of oxygen-absorbing resin compositions prepared by mixing iron-based oxygen absorbing agents with thermoplastic resins, packaging vessels and the like have been developed in such a way that the gas barrier property of the vessels and the like is achieved and the oxygen absorbability is imparted to the vessels themselves (see Patent Literature 1). Specifically, an oxygen absorbing multilayer film includes, as the case may be, additionally an oxygen absorbing layer which is a thermoplastic resin layer including an oxygen absorbing agent as dispersed therein, through an intermediate layer formed of a thermoplastic resin, between conventional gas barrier multilayer films each including a heat seal layer and a gas barrier layer as laminated on each other; such an oxygen absorbing multilayer film is used as a film to which a function to absorb oxygen inside a vessel in addition to the function to prevent the permeation of oxygen from outside, and produced by heretofore known production methods such as extrusion lamination, coextrusion lamination and dry lamination. However, such vessels also have a problem such that such vessels are detected by metal detectors used for foreign matter inspection for food and the like, cannot be heated with microwave ovens, and can develop the effect thereof only for the objects to be stored which are high-moisture systems. An oxygen absorbing multilayer film using an oxygen absorbing agent such as iron powder suffers from problems such that such an oxygen absorbing multilayer film is detected by a metal detector used for foreign matter inspection for food and the like, is insufficient in internal visibility due to opacity, and induces flavor degradation of the content because of the generation of aldehyde from the oxidation reaction of alcohol with iron as a catalyst when the content is an alcoholic beverage.
From the aforementioned circumstances, oxygen absorbing agents including an organic substance as a main reaction agent are demanded. As the oxygen absorbing agent including an organic substance as a main reaction agent, an oxygen absorbing agent including ascorbic acid as the main agent is known (see Patent Literature 2).
On the other hand, an oxygen-absorbing resin composition being composed of a resin and a transition metal catalyst and having an oxygen-capturing property is known. For example, a resin composition is known which is composed of a polyamide, in particular a xylylene group-containing polyamide as an oxidizable organic component and a transition metal catalyst (see, Patent Literature 3). Additionally, this Patent Literature 3 quotes as examples, for example, packaging materials obtained by molding resin compositions.
As an oxygen-absorbing resin composition requiring no moisture for oxygen absorption, an oxygen-absorbing resin composition composed of a resin having carbon-carbon unsaturated bonds and a transition metal catalyst is also known (see Patent Literature 4).